The disclosure relates generally to systems and methods for reducing pressure pulsations in systems pressurized by a reciprocating pump. More particular, the disclosure relates to a hydraulic system for controlling the discharge pressure of and reducing pressure pulsations in systems pressurized by a triplex reciprocating pump.
To form an oil or gas well, a bottom hole assembly (BHA), including a drill bit, is coupled to a length of drill pipe to form a drill string. The drill string is then inserted downhole, where drilling commences. During drilling, fluid, or “drilling mud,” is circulated down through the drill string to lubricate and cool the drill bit as well as to provide a vehicle for removal of drill cuttings from the borehole. After exiting the bit, the drilling fluid returns to the surface through an annulus formed between the drill string and the surrounding borehole wall. Instrumentation for taking various downhole measurements and communication devices are commonly mounted within the drill string. The instrumentation and communication devices operate by sending and receiving pressure pulses through the annular column of drilling fluid maintained in the borehole.
Mud pumps are commonly used to deliver drilling fluid to the drill string during drilling operations. Many conventional mud pumps are of a triplex configuration, having three piston-cylinder assemblies driven out of phase by a common crankshaft and hydraulically coupled between a suction manifold and a discharge manifold. During operation of the mud pump, each piston reciprocates within its associated cylinder. As the piston moves to expand the volume within the cylinder, drilling fluid is drawn from the suction manifold into the cylinder. After the piston reverses direction, the volume within the cylinder decreases and the pressure of drilling fluid contained with the cylinder increases. When the piston reaches the end of its stroke, pressurized drilling fluid is exhausted from the cylinder into the discharge manifold. While the mud pump is operational, this cycle repeats, often at a high cyclic rate, and pressurized drilling fluid is continuously fed to the drill string at a substantially constant rate.
Because each piston within the piston-cylinder assemblies of the mud pump directly contacts drilling fluid within its associated cylinder, loads are transmitted from the piston to the drilling fluid. Due to the reciprocating motion of the piston, the transmitted loads are cyclic, resulting in the creation of pressure pulsations in the drilling fluid. The pressure pulsations disturb the downhole communication devices and instrumentation by degrading the accuracy of measurements taken by the instrumentation and hampering communications between downhole devices and control systems at the surface. Over time, the pressure pulsations may also cause fatigue damage to the drill string pipe and other downhole components.
Accordingly, there is a need for an apparatus or system that reduces pressure pulsations created within fluid pressurized by a reciprocating pump due to contact between the pump piston and the fluid.